The following are diamond sizes with corresponding mm sizes. Be very aware that the following millimeter sizes are based on 60% depth with normal girdles and angles. This of course would be completely inaccurate if the diamond in question varied outside of those parameters.

Approximate Carat Weight Common Trade Jargon Millimeter Size
0.005 half-pointer 1.00 mm
0.01 one-pointer 1.30 mm
0.02 two-pointer 1.70 mm
0.03 three-pointer 2.00 mm
0.04 four-pointer 2.20 mm
0.05 five-pointer 2.40 mm
0.06 six-pointer 2.60 mm
0.07 seven-pointer 2.70 mm
0.08 eight-pointer 2.80 mm
0.09 nine-pointer 2.90 mm
0.10 ten-pointer 3.00 mm
0.11 eleven-pointer 3.10 mm
0.12 twelve-pointer 3.20 mm
0.13 thirteen-pointer 3.28 mm
0.14 fourteen-pointer 3.37 mm
0.15 fifteen-pointer 3.45 mm
0.16 sixteen-pointer 3.53
0.17 seventeen-pointer 3.60 mm
0.20 twenty-pointer, fifth 3.80 mm
0.25 twenty-five-pointer, quarter, one-grainer 4.10 mm
0.33 thirty-three-pointer, third 4.50 mm
0.38 thirty-eight-pointer, three-eighths 4.70 mm
0.42 forty-two-pointer, three-eighths 4.86 mm
0.45 forty-five-pointer, three-eighths 4.97 mm
0.47 forty-seven-pointer, light-half 5.05 mm
0.50 fifty-pointer, half, two-grainer 5.15 mm
0.55 fifty-five-pointer, half, two-grainer 5.32 mm
0.60 sixty-pointer, five-eighths 5.47 mm
0.65 sixty-five pointer, light three-quarter 5.62 mm
0.70 seventy-pointer, three-quarter, three-grainer 5.76 mm
0.75 three-quarter, three-grainer 5.90 mm
0.80 three-quarter, eighty-pointer 6.03 mm
0.85 heavy three-quarter, eighty-five pointer 6.15 mm
0.90 light carat, ninety-pointer 6.27 mm
0.95 light carat, ninety-five-pointer 6.38 mm
1.00 one carat, carater, four grainer 6.49 mm
1.10 one carat, carater, four grainer, carat-ten 6.70 mm
1.15 carat fifteen 6.80 mm
1.20 carat twenty, one and a fith 6.90 mm
1.25 carat twenty-five, on and a quarter, five grainer 6.99 mm
1.30 carat thirty, one and a third 7.09 mm
1.35 carat thirty-five, one and a third carat 7.17 mm
1.40 carat fourty 7.26 mm
1.50 carat and a half, one-fifty, six grainer 7.43 mm
1.65 carat sixty-five 7.67 mm
1.75 carat seventy-five, one seventy-five, seven grainer 7.82 mm
1.90 carat ninety, one-ninety, light two carat 8.04 mm
2.00 two carat, two carater, eight graner 8.17 mm
2.25 two and a quarter, two twwnety-five, nine grainer 8.50 mm
2.50 two and a half, two fifty, ten grainer 8.81 mm
2.75 two seventy-five, two and three quarters 9.09 mm
3.00 three carat, three carater 9.36 mm